Emergency oxygen supply systems are installed on aircraft to supply oxygen to passengers upon loss of cabin pressure at altitudes above about 12,000 feet. The emergency oxygen supply devices typically include a source of supplemental breathable oxygen connected to a face mask that is released from an overhead storage compartment when needed. The flow of breathable oxygen should be sufficient to sustain passengers until cabin pressure is reestablished or until a lower, safer altitude can be reached.
The Federal Aeronautics Administration (FAA) requires that emergency oxygen supply systems be shut off at the high pressure source whenever the aircraft is on the ground for an extended period of time. The FAA also requires that, as part of preflight procedures, the oxygen be turned on before take-off.
Typically, the high pressure shut-off valve is attached to a cylinder of pressurized oxygen located in the tail section of the aircraft. Operation of this valve is generally accomplished from a remote location, most often from the cockpit of the airplane. Current designs to accommodate the FAA requirement generally include a system of cables that are tied to a lever in the cockpit. To actuate the valve, the pilot pushes or pulls the lever, thereby moving a cable attached to the valve located in the tail of the aircraft. Such cable systems have potential disadvantages, for example, binding during operation.
The following patents and patent applications, the disclosures of which are incorporated herein by reference, describe a variety of valve assemblies for controlling the flow of a gas:
UK Patent Application GB 2193644 discloses a combined gas release and gas pressure measuring device connected to a pressurized gas cylinder and preferably used together with a breathing mask and flexible hood. Gas is released from the cylinder by gripping a knob and moving it to break a seal in a gas delivery tube. Gas pressure is measured by a Bourdon tube included in the device.
US Patent Application US 2007/0017573 describes an electromechanical system for regulating passenger oxygen flow during flight, the electronic portion of the system including inlet and outlet solenoid valves that enable the system to automatically revert to mechanical operation in the event of electronic or power supply failure.
US Patent Application US 2004/0154668 describes a gas control assembly that is mountable in the neck of a pressure vessel and extendable into the vessel interior, and includes a relief device that permits the exhaust of fluid from the vessel in the event of temperature and/or pressure exceeding a preselected value.
US Patent Application US 2006/0065303 describes a safety valve for a tank of pressurized gas that includes a check valve within the tank opening that operates to shut of the flow of gas in the event of a damaging lateral impact.
U.S. Pat. No. 5,040,559 describes an apparatus for controlling gas flow between an input port and an output port that comprises a valve between the input and output ports, a first actuating mechanism for operating the valve to control the gas flow rate between the input and output ports, and a second actuating mechanism for closing the valve and shut off flow between the ports, the second actuating mechanism being constructed to be selectively disengaged from the valve to permit the first actuating mechanism to operate the valve.
U.S. Pat. No. 5,100,100 describes a fluid control and shutoff valve assembly having a single valve that includes a valve body, a valve seat, and an actuator that includes an electromechanical force generating device, the valve body and seat being movable relative to one another in response to an electrical signal.
U.S. Pat. No. 3,219,052 describes a back pressure regulator valve assembly that includes a poppet type main valve urged into engagement with a seat by a low-rate spring and having an inlet end connected to a tank and an upper end located in a cavity under pressure from the tank, thereby maintaining the valve in a closed position. A pilot valve associated with the main valve functions, upon an increase in tank pressure above a predetermined value, to relieve the pressure on the upper end of the main valve, allowing the poppet to disengage from the seat and permitting a flow of gas through the main valve to relieve the pressure in the tank.